The overall objective of this project is to investigate the comparative biochemical and morphological aspects of the aging process in human erythrocytes during "normal" aging and during the accelerated aging that accompanies their exposure to agents which induce alterations in membrane structure and function. There are several unique aspects to the proposed research. For example, we propose to maintain red cells in sterile culture for prolonged periods of time at 37 degrees C. In this phase of the experimental work we will define the nutritional requirements of these cells during incubation for periods of up to two weeks. A second unusual aspect of this project results from our previous findings that thyroid hormones may participate in the initiation of free-radical reactions which induce membrane alterations affecting cell survival. We propose to define the nature of the effects of such hormones on membrane structure and function under the steady-state conditions of the prolonged culture system at physiological temperatures. Lastly, we propose to investigate the role of membrane loss by internal vesiculation in the aging process. In all of these experiments we will utilize a variety of biochemical techniques, freeze fracture, scanning and transmission electron microscopy of treated and untreated cells. It is our view that the proposed experiments are of interest with respect to the special problems of accelerated red cell aging in some hemolytic disorders which are expressed as anemia and also with respect to general theories of aging which postulate a role for free-radical mechanisms.